Designing quaternized di-N-chloramine silicone with synergistic biocidability for CO2-asssisted interpenetration into cellulose

A highly efficient biocide and an easily applicable procedure are two keys for antibacterial modification of cotton cellulose. A quaternized di- N -chloramine silicone that contains complementary functionalities of one quaternary ammonium salt (QAS) and two N -chloramine sites (an amidic one and an imidic one) in each composite unit was synthesized to better contact with bacteria to exert super biocidability. Briefly, Knoevenagel condensation between hydantoin with 4-dimethylaminobenzaldehyde produced a compound with one amidic and one imidic nitrogens and one tertiary amine. The tertiary amine of the Knoevenagel product was quaternized with 3-chloro-1-propanol whose hydroxyl group was subsequently bonded to poly(methylhydrosiloxane) via silane alcoholysis. The silane alcoholysis product was interpenetrated into cotton cellulose at 50 °C and 28 MPa in supercritical CO 2 (scCO 2 ) and its amidic and imidic nitrogens were then chlorinated to form a 76 nm quaternized di- N -chloramine silicone layer. Biocidal assay proved that QAS and N -chloramine sites functioned synergistically, eliminating ~ 7 log of S. aureus and E. coli at a much faster rate (in 3 min) than each functionality. The scCO 2 interpenetration produced a durable modification layer as shown by stability tests without the reliance upon chemical linkages and hence can be transferable to substrates with different components. Graphical abstract